The larger-than-life but now (literally) retiring Microsoft boss Steve Ballmer has been roundly trashed online over the past few days. Suffice it to say that if Ballmer were a play, it wouldn't have survived for a second night, let alone 33 years.

Yes, he made some painful mistakes. But on any rational judgement, Ballmer has been one of the world's most successful businessmen, and built what is still one of the world's top 10 companies by value. Much of Microsoft's success is down to Bill Gates, but the two friends have worked as a deadly duo since 1980, when Microsoft was a tiny, 29-man company. Ballmer deserves some credit for that, besides his $15 billion-worth of stock.

Since becoming CEO in 2000, Ballmer has more than tripled Microsoft's annual sales (from $23 billion to $78 billion) and more than doubled profits ($9.4 billion to $21.9 billion). In that time he's returned $164 billion to shareholders while adding around $90 billion to Microsoft's net assets. Very few CEOs have done better. Many tech companies — AMD, Dell, HP, Intel, Nokia, Sony, Sun etc — have done worse under multiple CEOs. Indeed, Ballmer has done much better than many people expected a dozen years ago.

As analyst Horace Dediu said at Asymco: "He did exactly what all managers are incentivized to do and avoided all the wasteful cannibalization for which they are punished."

Ballmer also established Microsoft as a powerhouse in server software and applications, transformed Windows, Office and Windows Mobile, acquired Skype and Dynamics, and with Azure, made a very strong move into cloud computing. Microsoft is still closing in on Ray Ozzie's vision of "three screens and a cloud", but the range and quality of its products is markedly better than when Ballmer took over.

Ballmer has managed all that in competition with free software — Linux, OpenOffice, Java etc — all of which were supposed to have killed Microsoft long before now. At least, that was the fanboy hype.

He has also managed it in a decade where Microsoft was under the constant close supervision of the US Justice Department and what looks like a vendetta from the European Commission. Hal Berenson, who left Microsoft in 2010, wrote in a blogpost:

"After the DoJ settlement, he had to spend a good chunk of his tenure finding a way to settle with the E.U. And then run the company under the terrible burden of complying with both settlements. Between the actual restrictions from these settlements and the general caution about antitrust that then pervaded the Microsoft culture, Steve was essentially running Microsoft with one hand tied behind his back.

"The truth is, I don’t think Steve gets enough credit for saving the company. Without him Microsoft probably would now be a footnote in tech history."

Of course, it's not all good news.

Ballmer hasn't been successful in important areas such as mobile phones, tablets and search in particular. However, looking at the Windows Mobile and Windows XP tablets that he inherited from Gates, hindsight suggests he didn't start from the best place.

Ballmer also failed to get the sort of devotion from Microsoft staff that Gates enjoyed, and that gets people to put in long hours and aim for the greatest possible outcomes. The hated stack ranking system obviously hasn't helped. Either way, Microsoft lost a lot of good staff. Worse, many of them went to rivals such as Google, and it shows.

But in the end, Ballmer's most obvious failure has been his public persona, which is one reason why he is being judged so harshly. In public, Ballmer has usually seemed the pumped-up football coach, and blustering can work pretty well with people who are on your team. However, it goes down really badly with your enemies, and on TV. Ballmer's an extremely smart guy (and, unlike Gates, actually graduated from Harvard), but that's not his image. And in an age of ignorance, most people take the image for the reality.

Gates managed to turn himself from a belligerent, squeaky-voiced kid into a man who could attract huge audiences at Comdex and CES — which Ballmer failed to do — and he's now become something of a saint. In contrast, Ballmer doesn't seem that much different after 33 years at Microsoft. He's still loud and gaffe-prone when he should have developed a more relaxed, avuncular twinkle.

Note that I don't blame Ballmer for Microsoft's flat share price over the past dozen years. Microsoft and many other tech companies were ridiculously overvalued in Bubble 1.0 around the turn of the century, and that kind of stupidity takes a very long time to unwind. The graph below shows how Microsoft's share price compares with other PC industry giants — Dell, HP, and Intel — after January 2001.

In the end, Ballmer's reign has been a bit of mixed bag, but a fair judgement must include both sides of the story. He could have done better, but he could have done one heck of a lot worse.